Display screen or portion thereof with an animated graphical user interface



FIG. 1 is a front view of a first image in a sequence for a display screen or portion thereof with an animated graphical user interface showing our new design; and,

FIG. 2 is a front view of a second image thereof.

The outermost broken-line rectangle illustrates the perimeter of a display screen or portion thereof and forms no part of the claimed design.

The remaining broken lines illustrate portions of a graphical user interface and form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-2. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM We claim the ornamental design for a display screen or portion thereof with an animated graphical user interface, as shown and described. 